1. Field of the Invention
This invention relates to the field of assembly devices operating by tension to draw frame members into proper alignment and to hold them firmly in place while they are being glued or otherwise fixedly joined together.
2. The Prior Art
The concept of achieving a clamping structure by encircling an assembly of wooden strips by a flexible binder element and applying tension to the binder to hold the strips firmly in place is described in U.S. Pat. No. 2,691,996. In that patent, an assembly of boards is held together to produce a hollow nold into which wet concrete may be poured to form a concrete column. The boards that constitute the mold extend in the longitudinal direction of the column and are held together by several frames, each consisting of wooden strips perpendicular to the boards. The wooden strips are not mitered, and the concept of self-jigging is not considered. One end of the flexible binder element is affixed to one corner member, or bed plate, that fits against two walls of the mounting frame at one of the corners, and the other end of the binder, after being wrapped almost entirely around the frame, is attached to a structure that is threadedly engaged with a bolt supported on the corner member to apply tension to the binder by rotation of the bolt. While the binder will apply tension to hold the wooden strips that constitute the mounting frame in place around the boards once the boards and mounting frame have been properly assembled, the lack of self-jigging of the wooden strips makes assembly undesirably difficult. The arrangement of the tightening bolt so that its axis is substantially parallel to one of the frame members would make the structure difficult to apply to assembly of a picture frame.
U.S. Pat. No. 3,224,754 shows a framing device in which a flexible binder encircles mitered frame members and is threaded through corner pieces at each corner. However the ends of the binder are connected to a turnbuckle located midway along one of the frame members so that the force of the turnbuckle is applied directly in line with the sections of the binder attached directly to it. This location of the turnbuckle requires that the handle of the turnbuckle be constantly worked back and forth as the turnbuckle body is rotated to increase tension in the binder. In each revolution of the turnbuckle, each end of the handle will come into contact with the frame member adjacent to which the turnbuckle is located, so that free rotation of the turnbuckle is impossible.
U.S. Pat. No. 3,610,612 shows a picture frame assembly structure that has four corner pieces to fit around the four corners of the frame. However one pair of these corner pieces is threaded onto a first guide rod and the other pair is threaded onto a second guide rod to assure that the respective pairs of corner pieces can only move longitudinally along the guide rods as a result of tensioning force applied to the corner members by a cord wrapped around them. The ends of the cord are wrapped around an axle parallel to one of the frame members when the frame members are assembled, and thus the tension in the cord is not properly distributed with respect to the frame members nor with respect to the axle.
U.S. Pat. No. 4,047,710 shows a framing clamp with corner members mounted in guide ways to assure that the frame members engaged by the corner members are assembled at the proper angles when force is applied to a binder that encircles all of the corner members. This complex structure does not properly make use of the self-jigging relationship of mitered frame members. In addition, the binder is wrapped around an axle alongside one of the frame member locations but spaced away from that frame member. The location of the axle about which the ends of the binder are bound makes use of a complex binding system.